George herbert xwhittingham



e H. WHITTINGHAM.

.AULTIVALUE OVERLOAD SWITCH. APPLICATION nun JUNE 17. 1918.

1 ,3 1 O, 380. Patented July 15, 1919.

UNITED STATES PATENT OFFICE.

GEORGE HERBERT WHITTINGHAM, OE BANCBOFT PARK, MARYLAND, ASSIGNOR TO MONITOR CONTROLLER COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND.

IllllU'LTIV'AL'UE OVERLOAD-SWI'I'CH.

To all whom it may concern:

Be it known that I, GEORGE H. WHITTING- HAM, a citizen of the United States, residing at Bancroft Park, in the county of Baltimore and State of Maryland, have invented certain new and useful Improvements in Multivalue Overload-Switches, of which th following is a specification.

This invention relates to multi-value overload cut-out switches for electric motors, adapted to interrupt the armature circuit if the motor is overloaded while running, but to maintain said circuit closed while the armature is carrying the excess current required for starting. In the present invention, in closing the switch, the core of a tripping solenoid is manually moved by an operating handle from its normal position Within the solenoid coil to a less effective position from which it cannot be moved by'the action of the starting current. The solenoid core will be held in this ineffective position as long as the operator holds the operating handle away from its normal position; but the core will return automatically to its normal position in a predetermined time after release of the handle, and the solenoid will then become effective as a tripping means for the switch if the armature circuit is overloaded while the motor is running. Thus, for ordinary uses, the operator may close the switch and immediately release the handle and the solenoid core will then be returned to its normalposition after a sufficient length of time has elapsed to permit the starting current to fall to normal; but in some cases, as where the load is heavy and the motor startsslowly, it may be desirable to prolong the time in which the solenoid is inefl'ective to-trip the switch, and the operator may accomplish this purpose by holding the operating handle away from its normal position for such time as he deems desirable.

In the accompanying drawing, Figure 1 is a side view of the overload protective device, the motor circuits being shown diagrammatically; and,

Fig. 2 is a top plan view of the device. Referring to the drawing, 1 indicates a solenoid, the coils of which are included in the armature circuit of the motor m, this circuit extending from the service switch 2, through conductor 3, to the coil of solenoid 1, thence through conductor 3 to a station- Speciflcation of Letters Patent.

Application filed June 17, 1918 Serial No. 240,342.

ary contact 4, thence through switch arm 5 to a shaft 6, on which said arm is mounted, thence by conductor 7, through a suitable automatic starter 8 to the armature a of the motor, and thence by conductor 9 to the service switch 2. 7 indicates the shunt field of the motor, connected by conductor 10 to conductors 7 and 9, as shown.

The solenoid has at its upper end a vertically movable pin 11, arranged beneath a pivoted latch 12, and within the solenoid, beneath said pin, is arranged a core 13, adapted, when the circuit is overloaded, to move upward and force the pin 11 against the'latch. Secured to the shaft 6 is a bowshaped arm 14, which is adapted to engage the latch 12 when the switch arm 5 is in engagement with the contact. 4. A U-shaped operating lever 15 is pivotally mounted upon the shaft 6 and extends upwardly in front offthe arm 14, and is provided with a handle 15. The operating lever is normally held against the stop 16 by a spring 17. When the lever 15 is moved to the left, it presses the arm 14 into engagement with the latch 12, and the switch arm 5, secured to the shaft 6, is pressed into engagement with the contact 4, thus closing the armature circuit of the motor. When the operator releases the lever, the latter drops back against the stop 16.

The core 13 of the magnet is supported upon a bow-shaped arm 18, which is journaled upon the shaft 6, and is normally held in an upper position by a spring '19, surrounding the piston rod 20 of a-dashpot 21, this rod being pivotally connected to the arm 18,, as shown. An adjusting screw 22 extends through the arm 18 and the solenoid core 13 rests upon this screw. The operating lever 15 is provided with arms 15 which project over the re-setting lever 18, and itwill be evident that when the operating lever is moved to close the switch, the arms 15 will rock the re-setting lever 18 downward against the action of the spring 19, and the solenoid core 13 will thereby be lowered. The dashpot piston 22 is arranged to move freely in the downward direction, but slowly in the upward direction, and

hence, when the operator releases the lever latch at any given overload current is found by adjusting the screw 22.

The operation of the invention is as follows. To start the motor, the operating lever is moved to the left, in Fig. 1, until the switch arm is in engagement with the contact 4.- and the arm 14 is in engagement with the latch 12. During this movement, the ire-setting arm 18 is rocked downwardly by the operating lever and the core '13 is thereb permitted to move downward into a less edective position within the solenoid core. In this position the normal starting current of the motor will not cause the core to lift and trip the latch;'but after the operating lever is released, the spring 19 moves the re-setting arm upward, against the retarding action of the dashpot until the core 13 is in its normal position within the sole- 20 noid. Thereafter, an overload current, of any predetermined value, will lift the core and the latter will move the pin 11 against the latch 9, causing the latter to trip from the arm 14 and thereby the switch 4-5 will be opened. It will be noted that the switch is closed and the solenoid core is lowered by a manual operation and that the core remains in its lowered position until the operating lever is released. Thus, the time interval required to re-set the solenoid core does not necessarily commence to run at the time of closure of the switch, but at the time of the release of-the operating lever. It is desirable, in some cases, as when the motor is operating under a heavy load, to prevent the operation of the trip for an indefinite time, while the motor is getting started, and with the manually operated device of this invention 40 the solenoidcore is held in its inefiective or inoperative position, after the closure of the switch, as long as the o eratpr desires, by holding the lever in the oft hand position.

, While the invention is shown in connection with a direct current motor and a single pole switch, it is obvious that several switch arms upon the shaft 6 maybe controlled by the same overload device, and that such switch arms'may be employed tobreak both to sides of the armature circuitof a direct current motor, or the several circuits of a threephase motor. It is also obvious that separate overload devices of the kind herein described may be placed in the several circuits, '55 of a three-phase motor. I

What I claim is:

switch arm normally in open position, a

latch for holding said arm in closed position, a solenoid for tripping said latch and comprising core and coil members, a support normally holding one of said members in a predetermined relation to the other member, and a manually operable member adapted to move the switch arm to closed position and said support from normal position, said arm, support and manually operable member being independently movable to their normal positions.

2. In a multivalue overload switch, a switch arm normally in open position, a latch for holding said arm in-closed position, a solenoid for tripping said latch and comprising core and coil members, a support normally holding one of said members in a predetermined relation to the other member, a manually operable member adapted to move the switch arm to closed position and said support from normal position, said arm, support and. manually operable member beingindependently movable to their normal positions, and means for retarding the movement of said support to its normal position.

3. In a multi-value overload switch, a switch arm normally in open position, a latch for holding said arm in closed position, a solenoid for tripping said latch, a

support for the solenoid core normally holding the core in position to be actuated by a given overload current, a manually operable member adapted to move the switch arm to closed position and said support from normal position, said arm, support and member being independently movable to their normal positions, and means for retarding the movement of said support to its normal position.

4:. In a multi-value overload switch, a switch arm normally in open position, a latch for holding said arm in closed position, a solenoid for tripping said latch, a support for the solenoid core normally holding thecore in position to be actuated by a given overload current, a manually operable member adapted to move the switcharm to closed position and said supportfrom normal position, said arm, support and member being pivotally mounted about at common axis and independently movable to their normal positions, and means for retarding the movement of. said support to its normal position.

In testimony whereof I aflix my signature.

GEORGE HERBERT WHITTINGHAM. 

